Photochromic polyacetylenes responsive to radiation exposure have been disclosed in several U.S. Patents, namely U.S. Pat. Nos. 4,066,676; 4,581,315; 3,501,302; 3,501,297; 3,501,303; 3,501,308; 3,772,028; 3,844,791, 3,954,816, 5,232,820, 5,731,112, 6,017,390, and 6,177,578. Of these polyacetylene compounds, including those of highest sensitivity, the recording of image or dosage information has presented several problems and shortcomings including an inadequate degree of resolution, clarity, color instability of an imaged pattern. The prior polyacetylene compounds appear to be incapable of forming stable radiation dosage indicia. Other deficiencies include a relatively slow image development, and, in some cases, the impractical need to image at extremely low temperatures or at excessively high dosage levels.
While lithium salts of various polyacetylene compounds have been mentioned as possible candidates for radiation image recording, they have not provided a desired radiation sensitivity or clarity in image recording demanded for commercial success.
Accordingly, it is an object of the present invention to overcome the above difficulties and deficiencies by the use of a specific group of polyacetylene compounds in a unique form and dimension to achieve an unprecedented high radiation sensitivity which is responsive to all forms of radiation including that generated by an electron beam, gamma rays, β-rays, x-rays, ion beam, ultra-violet and visual light generated from actinic radiation in the visible and infra-red regions of the electromagnetic spectrum and other forms of corpuscular and/or wave-like energy generally deemed to be forms of radiant energy.
Another object of the invention is to maximize radiation sensitivity of a lithium/polyacetylene salt in a filamentary state.
Another object is to employ a highly sensitive radiochromic lithium salt of a polyacetylene as a coating on a substrate or as a powder or tablet.
Yet another object is to provide an economical and commercially feasible method for preparing the lithium salts of this invention.
Still another object is to provide improved method for two- or three-dimensional imaging.
These and other objects and advantages of the invention will become apparent from the following description and disclosure.